A copyholder can comprise a base, a plurality of mutually articulated arms cantilevered to the base, a copy support plate or thelike mounted at the free end of the cantilevered arm.
The cantilevered arm is usually pivotable about the base, the cantilevered arm segments being pivotable with respect to each other, while the copy support plate is pivotable on the cantilevered arm.
The pivotability can be controlled by a plurality of manually adjustable pivot joints which are at least frictionally controlled by a securing mechanism associated with each pivot joint. At least one handle, which acts on a plurality of securing mechanisms associated with the pivot joints by way of at least one intermediate member can be positioned at least adjacent the copy support plate. The intermediate members and the securing mechanisms can be arranged inside of the cantilevered arm segments, and a tension or traction line (cable, cord or rope) which crosses the central pivot axes is provided as at least one of the intermediate members.
This kind of copyholder is described in U.S. Pat. No. 1,460,697 and allows a sketch, paper or the like to be brought into a position beneficial to the user in a particular working environment. Thus the base can be constructed as a heavy stand for example. Also instead of a stand on the base a clamping holder for attachment of the copyholder, for example, to a table edge, may be provided, whereby the base can be supported to pivot about a vertical axis.
The cantilevered articulated arm comprises at least two cantilevered arm segments positioned one after another in succession, These arm segments adjust the height of the copyholder by pivoting the cantilevered arm segment individually, and the distance the cantilevered arm is extended, i.e. the range of the copyholder.
Moreover it may be necessary to change the position of the cantilevered arm by disengaging the securing mechanisms associated with the pivot joints by loosening of the handle and therefore the traction line. The copy support plate may then be brought into the desired position and subsequently the securing mechanisms may be relocked.
In prior art copyholders individual segments of the traction line found between the frictionally or otherwise controlled securing mechanisms are under tension or stretched to attain a pivot-blocking force and friction whose magnitude is determined by the tension, so that a substantial force must be applied to the handle in order to secure the pivot joints.
It is also known in the prior art to associate each pivot joint with an additional manually operable clamping mechanism.